In the manufacture of motor vehicles, it is the practice to attach fixed glass panels (i.e windshields, taillights, rear window panels, and certain side window panels on automobile, truck and bus bodies) to the vehicle body by means of a thick bead of elastomeric sealant material. The sealant materials which are used for this purpose are required to meet a number of criteria including appearance, ease of application, shear strength, and adhesion in crash tests. The window sealant compositions are often applied directly over the paint coating finishes on the motor vehicle body. This means that good adhesion both between the sealant composition and the paint coating and between the sealant composition and the glass panel is required. Sometimes, a weaker than desired bond is formed between the sealant bead and the paint coating and the sealant bead delaminates from the underlying paint layer. This can lead to isolated leaks between the window panel and the motor vehicle body or, at worst, total failure of the bond between the motor vehicle body and the fixed window panel.
To promote adhesion between the sealant composition and a substrate and non-porous materials such as glass, ceramic, or composite materials, a number of sealant primer compositions have been disclosed in the prior art in areas relating to motor vehicle manufacture as well as other areas.
For example, United States Patent 3,707,521 to De Santis, and its divisional, U.S. Pat. No. 3,779,794, disclose a polyurethane sealant primer composition comprising a branched polyurethane polymer in combination with a latent catalyst for the moisture curing of free isocyanate groups present.
U.S. Pat. No. 3,872,047 to Jandourek discloses a sealant primer composition comprising a polymer having high polar hydrophilic groups and low polar hydrophobic groups for bonding dental restorative materials to metalion containing substrates.
U.S. Pat. No. 3,033,833 to Le Fevre, et al. discloses interpolymers of l-sulfoalkyl esters of alkylacrylic acids and other polymerizable ethylenically unsaturated compounds having utility, for example, in preparing surfaces to better receive dyes.